Advanced integrated circuit technology continues to create new challenges as components and architecture are reduced in size. Communication between different levels deposited on a substrate has become more complex since the size of the features, typically vias, connecting the different levels has changed in size and shape, especially the aspect ratio. By via it is meant an area created by either etching away a portion of a layer so that a `hole` is created or an area created by the deposition of raised portions that define the walls of the area. For the remainder of the discussion, a feature will be referred to as a via.
The aspect ratio of a via is a measure of the height (H) compared to the width (W). If a via is wide and shallow, the aspect ratio is less than 1, H/W&lt;1. If a via is narrow and deep then the aspect ratio will be greater than 1, H/W&gt;1.
After a via is created it usually is filled with a material. Filling a via with an H/W&lt;1 is well understood in the art and can be efficiently done with known techniques. However, filling a via with an H/W&gt;1 still presents a challenge. As shown in FIG. 1, when the aspect ratio is greater than 1, the via, 1, has the shape of a rectangle with the length of the bottom of the rectangle (W), 2, at most equal to the length of the sidewalls (H), 3. Current via filling techniques must be followed with precision to fill vias with an aspect ratio approaching 1. There is little margin for error when filling high aspect ratio vias where the ratio is greater than 1. As the value of H/W increases even the most precise methods might not produce reliably filled vias. As shown in FIG. 2, the shape of void portion, 5, of a via, 1, may, for example, be tear-shaped. The two side portions covering the walls of the via, 5a and 5b, may, for example, be in the shape of the tear, where one side of the void area, 5, is open at the surface, 5c. The two side portion covering the walls of the via, 5a and 5b, may or may not be perpendicular to the bottom of the via and also may or may not be in contact with each other. When the tops of the two side portions, 5a and 5b are in contact with each other "pinchoff" is said to have occurred.
Current methods of filling high aspect ratio vias involve deposition techniques like high temperature sputtering, chemical vapor deposition (CVD) and forceful. Most, if not all, of these techniques fill vias in such a way that it is requires either a high temperature or expensive methods.